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In Reply to: RE: Favorite Tubes for DIY posted by Neff on June 29, 2008 at 05:42:40
Dude,
You are overlooking a valuble resource, NOS Locktal based tubes. The 7Z4 will go where a 6V4/EZ80 goes. The 7Y4 goes where a 6X4 goes. The 7N7 is electrically equivalent to the 6SN7. The 7F7 is electrically equivalent to the 6SL7. The 7AF7 is another terrific medium mu twin triode, with a smaller heater draw than the 6SN7 family. The "14" series Locktals, with their "12" V. heaters, are even less costly than the "7" series tubes.
I fully agree with your assessment of the 6V6, in triode mode. The entire family: Octal, Loctal, Noval, and 7 pin mini tubes are a superb resource. Aside from the NOS, New Sensor offers 2 FINE current production 6V6 varieties, that carry the EH and TungSol labels. BTW, the 6V6 family is highly satisfactory in UL and pentode modes, as well as triode mode.
Eli D.
Follow Ups:
Yep, My PP 300B, 45, etc, sit quietly while I amaze myself at what the 6v6 in triode offers with a cool driver. While I am sure 1w is pushing it in my system now, it has been a month or so & really don't turn the dang thing off. 27 as driver & 3/4 done with a IT coupled version that has Hashimoto H-20-7U installed & awaiting O'Netics level II from Bud P, for the IT. Into some modded JBL SR4725's. The RC version has the best electric guitar tone I have ever heard. I feel I might have broke free from 300B etc....I'll be bringing this simple little amp to VSAC next year & run it without embarrassment.
J & G
Hi Eli,
I would like to ask who currently makes a good 6V6 amp. You guys have my interest up. Thanks.
Search for Poindexter.
His amp is supposed to be not just a great 6V6 amps, but one of the better amps around (in ANY kind of a reasonable price range).
I built a variation of the music machine. I changed the input tube to a Sylvania 6SN7. My version used four inexpensive PPP 6AQ5 per channel for about 10 watts output with 280 volts on the 6AQ5 plates or a little over spec.
> > I would like to ask who currently makes a good 6V6 amp. < <
Poindexter's "Musical Machine" is a very serious assault on "state of the art" performance. If you have the requisite coin of the realm, build a "Machine" yourself or commission Poinz to do it for you.
A much more budget conscious design is "El Cheapo". EC yields lots of good sound, for surprisingly little money. Are you ready to "sling" solder? :> ))
Eli D.
Old 1940s era 7C5 are a great option for 6V6GT tubes that can be expensive.
Screen grid fragility makes the 7C5 awfully close to the 6AQ5.
Google El Leako to see a Leak Stereo 20 converted into an "El Cheapo" style amp. SHiFTY did some very nice work. He used 7C5s as the O/P tubes. ;> )
Eli D.
Google El Leako to see a Leak Stereo 20 converted into an "El Cheapo" style amp. SHiFTY did some very nice work. He used 7C5s as the O/P tubes. ;> ) > >
I tried to find a picture, but no luck. You can do a lot with a Stereo 20 - mine has PPP 6S4 outputs and an ECC40 driver!! Next one will go all-DHT. May use 1624 outputs for that, but you really need something thinner to fit the chassis. Maybe 7C5 outputs and 3a5 in. That should be tasty, but would need a preamp.
Andy,
SHiFTY posted some pictures in the "El Cheapo" saga. A direct link is provided below. Notice the "gorilla" of a filter choke that was added to the OEM "iron" set. IIRC, our "Kiwi" friend also posted photos over on DIY Audio.
The low mu and low gm of the 3A5 argue against it being used as a LTP. However, the amount of loop NFB needed here is low. Linearizing the O/P trafo is the principal target. Perhaps Williamson style circuitry using the 3A5 after the "concertina" phase splitter is indicated. You're the expert on DH types, not me. Is there a good sounding single, modest mu, small signal DHT in your "pile"? I'm thinking of a strange, but likely palatable, "cocktail". DHT voltage gain DC coupled to a (SIC) ZVN0545A "split load" phase splitter holds the bottle count down to a reasonable level.
Eli D.
Notice the "gorilla" of a filter choke that was added to the OEM "iron" set. > > >
Absolutely gross - destroys the look. Yuk!
<>
I don't use loop feedback.
<>
Morgan Jones has a clever rewiring scheme for the OPT to make it sound better - hard wires the secondaries for 4 ohms.
< < < Perhaps Williamson style circuitry using the 3A5 after the "concertina" phase splitter is indicated.> >
I like to have a balanced in option, so I use a diff pair with CCS under it. I use the ECC40 if I need more gain and only have room for one stage, or I rely on some gain in the preamp if I just use DHTs.
< < You're the expert on DH types, not me. Is there a good sounding single, modest mu, small signal DHT in your "pile"? I'm thinking of a strange, but likely palatable, "cocktail". DHT voltage gain DC coupled to a (SIC) ZVN0545A "split load" phase splitter holds the bottle count down to a reasonable level.> >
Not really - there are a few DHTs with higher gain but the plate resistance gets silly - see 1H5, 3a/142A, 3a/108, DC80, 826, 1G6G. No - the thing to do is just use three stages in the amp, like 01A, 10Y, 300b. It's a predictable combination but it sure as hell works! Andy
I did not know that about 7C5 marginal screens. I have run trioded 7C5s fairly hard with 340 volts plate & 35 ma plate current. I did not see a glowing screen as I always take a peek inside power tubes. Perhaps the difficult angle prevented that on the 7C5 due to large top getter.
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